Charged particle beam apparatuses have many functions in a plurality of industrial fields, including, but not limited to, inspection of semiconductor devices during manufacturing, exposure systems for lithography, detecting devices and testing systems. Thus, there is a high demand for structuring and inspecting specimens within the micrometer and nanometer scale.
Micrometer and nanometer scale process control, inspection or structuring is often done with charged particle beams, e.g. electron beams, which are generated and focused in charged particle beam devices, such as electron microscopes or electron beam pattern generators. Charged particle beams offer superior spatial resolution compared to, e.g. photon beams due to their short wavelengths.
Besides resolution, throughput is an issue of such devices. Since large substrate areas have to be patterned or inspected, throughput of, for example larger than 10 cm2/min are desirable. In charged particle beam device, the throughput depends quadratically on the image contrast. Thus, there is a need for contrast enhancement.
High resolution electron optics systems require a short working distance between the objective lens and the wafer. Secondary electron collection is therefore typically done inside the column above the objective lens. A configuration commonly found in prior-art electron-beam imaging systems is shown schematically in FIG. 1. A column having length 104 including an emitter 105, an objective lens 10 and an annular secondary-electron detector 115, are spaced at a working distance 120 from a specimen 125. Primary electron beam 130 from emitter 105 is directed at specimen 125 through an opening 135 in annular detector 115. Secondary electrons 140 are emitted from specimen 125 in a broad cone surrounding primary beam 130. Some of secondary electrons 140 are collected by detector 115 to produce a secondary-electron (SE) signal 145.
Further, it is desired for many applications that the imaging information is increased while high-speed detection is provided. For example, upon irradiation of a sample by a primary beam of electrons, secondary electrons (SE) are created which carry information about the topography of the sample, its chemical constituents, its electrostatic potential and others. High speed detection provided with topography information and/or information on the energy of the secondary particles is a challenging task, for which continuous improvement is desired. Accordingly, improvements of the detection in the SEM-based tools, particularly in high throughput defect inspection or review tools, is desired. Additionally or alternatively, separation of several signal beam bundles, e.g. with reduced cross-talk, is desired for detection of topography imaging or the like.